Our Oranda developed sort of red streaks in her tail that lead to what looked like a small White blister. This blister then seemed to burst and looked red and sore and the bit of her fin it was on looked a bit raggedy. I did 2 large 50% water changes one day after the other, then 2 25% water changes the 2 following days. The nitrate is down to around 10. I've also been adding aquarium salt but am not sure if I do this after every wAter change bearing in mind I'm doing loads at the moment. She looks happier and I THINK the fin looks less inflamed and the streaks not as red. Anything else I can do? Thanks!